CVE-2026-42191: open-telemetry opentelemetry-dotnet

Vulnerability summary

CVE-2026-42191 is a high (CVSS 7.8) vulnerability in open-telemetry opentelemetry-dotnet. EPSS estimates a 0.15% chance of exploitation in the next 30 days, higher than 3.6% of scored vulnerabilities.

Timeline

1. 12-05-2026
   PublishedVulnerability first disclosed.
2. 13-05-2026
   Last modifiedVulnerability information updated.

Description

OpenTelemetry.Exporter.OpenTelemetryProtocol is the OTLP (OpenTelemetry Protocol) exporter implementation. From 1.8.0 to 1.15.2, the OTLP disk retry feature in OpenTelemetry.Exporter.OpenTelemetryProtocol silently fell back to Path.GetTempPath() when OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY=disk was set but OTEL_DOTNET_EXPERIMENTAL_OTLP_DISK_RETRY_DIRECTORY_PATH was not configured. The exporter stored and loaded *.blob files under fixed, signal-named subdirectories (traces, metrics, logs) beneath that shared temporary root path. On multi-user systems where the temporary directory is accessible to other local accounts, this allows an attacker to write crafted *.blob files, read *.blob files written by the application between export failures, or deposit numerous or oversized blob files, degrading retry-loop performance or consuming disk space. This vulnerability is fixed in 1.15.3.

• CWE-379Creation of Temporary File in Directory with Insecure PermissionsThe product creates a temporary file in a directory whose permissions allow unintended actors to determine the file's existence or otherwise access that file.